Chlamydia trachomatis (CT) is the leading cause of tubal obstruction and infertility in the US and globally. Similar to humans, primary chlamydial infection in rodent models induces immunity that is partially protective against subsequent challenge. IFN?-producing CD4 T cells (Th1 cells) are essential for resolving infection and resisting reinfection. CD8 T cells can contribute to resolution through production of IFN?, and antibodies augment resistance. Studies in mice and guinea pigs demonstrated that the induction of Th1 cells in the FGT by infection or vaccination correlate with protection. Tissue resident memory IFN?-secreting CD4 T cells (Th1 TRM) were shown to be critical for long-term immunity in mice. These findings support our hypothesis that an efficacious chlamydial vaccine will therefore need to induce both systemic Th1 and FGT Th1 TRM. Animal models are essential for iterative testing of vaccines to provide essential immunogenicity, mechanistic, and efficacy data for progressing vaccines to the clinic. We have standardized mouse and guinea pig genital tract challenge models for testing chlamydial vaccines. We will examine two leading T cell vaccine modalities proven safe in humans for the development of novel chlamydial vaccines. The first is a heterologous virus vector prime boost regimen comprised of a chimpanzee adenovirus (ChAd) prime followed by a Modified vaccinia virus Ankara (MVA) boost shown to induce high frequencies of CD4 and CD8 T cells. We will generate and test the first ChAd/MVA vaccines against chlamydia. The second platform uses a proprietary nanoemulsion Nanovax? to adjuvant recombinant proteins. Nanovax? vaccines are specifically formulated for intranasal delivery and efficiently induce mucosal CD4 T cells and antibodies. We will develop and test trivalent Nanovax? vaccines against Chlamydia. The immunogens used will be species-specific homologs of CT proteins that have documented immunogenicity in women who resisted reinfection or limited the extent of their CT infection. We will use these vaccine modalities to pursue three specific aims: Aim 1. Evaluate the immunogenicity and protective efficacy of replication-deficient viral vectors expressing chlamydial antigens in mice. Aim 2. Evaluate the immunogenicity and protective efficacy of recombinant chlamydial antigens delivered intranasally via NE in mice and the ability of combined vaccines to improve protection. Aim 3. Determine the immunogenicity of ChAd/MVA prime-boost and NE- adjuvanted chlamydial vaccines in female guinea pigs and their ability to protect from artificial and sexual transmission of C. caviae alone and in combination. This project will identify novel chlamydial vaccines with a highly feasible path to clinical testing and licensure.